With an increase in integration degree of ICs in recent years, lighting optical apparatuses using deep ultraviolet light sources with shorter wavelengths are growing in importance. This is because making wavelengths of a light source in an exposure device of LSI or a sample inspection apparatus shorter generally leads to improved resolution. Moreover, a lighting optical apparatus needs to illuminate an irradiated plane with uniform illumination distribution and, for this purpose, an integrator optical system is known to be effective (for example, JP-A 2006-98156 (KOKAI)).
FIG. 4 exemplifies an integrator optical system of a conventional lighting optical apparatus. FIG. 4A is a sectional view on an XZ plane and FIG. 4B is a sectional view on a YZ plane. Cylindrical lenses 40 and 44 have a cylinder axis directed in the Y axis and thus have no curvature on the YZ plane. Cylindrical lenses 42 and 46, on the other hand, have a cylinder axis directed in the X axis and thus have no curvature on the XZ plane. A ray 50 emitted from a deep ultraviolet light source 48 and incident from the left side are split in the X direction by the cylindrical lens 40 and in the Y direction by the cylindrical lens 42. Such a plurality of split light fluxes is superimposed on an irradiated plane 54 by a condenser lens 52 to form uniform illumination distribution.
Here, the cylindrical lenses 44 and 46 assume a role of a field lens that aligns directions of a plurality of light fluxes that, after passing through the cylindrical lenses 40 and 42 respectively, are incident. If a ray whose component is not in parallel with the ray 50 incident on the cylindrical lenses 40 and 42 is partially mixed, some light fluxes whose direction is not aligned arise in the plurality of split light fluxes emitted from the cylindrical lenses 40 and 42. Thus, a problem arises that illumination distribution on the irradiated plane 54 becomes non-uniform. The problem is solved by the plurality of light fluxes being aligned by the field lens.
The present invention has been developed in view of the above circumstances and an object thereof is to provide a lighting optical apparatus and a sample inspection apparatus using a deep ultraviolet light source that provide high illuminant and highly uniform illuminant on an irradiated plane.